Her Brother Slapped Their Mum Twice. Should She Arrest Him?

Franca shared her story on Nairaland. What are your thoughts on this?:

A friend of mine called me this morning to explain her ordeal when her brother slapped their mum twice last night. I was confused on the issue. We need your advice urgently. Here's what happened: 

His name is Oscar. In 2006 after finishing his NYSC he looked for a job for 2 years without success. During his NYSC year he served in Lagos and started dating a girl, Tania. After NYSC, they were still dating. This girl has an OND. She works at one of the major Accounting/management firms in Nigeria. In 2008, her company was employing. And she told her bf, Oscar. That's how he got his job with the company. He moved to lagos and she offered that he moves in to her one room self contain apartment. 

So he got a job with free accommodation. He has really gone far in his job. He is now in middle management. He even has an M.Sc now. Went to LBS. He built a house for his family in Delta. They moved in this year. The wahala is that the mum hates the girl, Tania. She sees no good about the girl. She says the girl's level of education is too low for her son. But the guy wants to marry her this year. 

He now lives in a bigger 3 bedroom flat in Lekki and she lives with him. The mum has always told the guy to send the girl out of his house. Yesterday, Oscar was expecting the mum. She was coming to visit for the weekend. While he was at work, she arrived in the evening. Tania just came back from work. To cut the long story short, the mum threw Tania out of the house. Packed all Tania's stuffs and dropped them outside the compound. After throwing Tania things outside, she swept the house. Tania called her fiancée after she left. The guy returned home to talk to his mum. The guy was angry that while they were talking the mum slapped him and he slapped her back twice and told her to leave his life alone. She called her family members and they are all against the son. She's still in his house but he packed a bag and left. They have not seen him since last night. His phone lines are not going through. 

My friend said the family is saying they should report at the station and police should start hunting for the guy. That he must suffer for his actions. What should she do? We need your advice. 

Update on this event: 

They were able to reach Oscar through one of his friends this early morning. Oscar said he never slapped his mum. He said she slapped him once and he was shouting at her not to try it again then she wanted to slap him again and he slapped her hand down. The palm of her hand. When she was throwing the slap, he slapped her hand down like he was blocking the slap. Then he went to his room packed a few things and to look for Tania who went to wait for him in their church.